An exemplary component that is supplied with analog values is a display panel.
Mobile phones, personal digital assistants (PDA) and many other electronic devices comprise a display panel for presenting information to a user. The display panel usually belongs to a display module. A common type of a display module is, for example, a liquid crystal display (LCD).
FIG. 1 presents an arrangement in an electronic device including such a display module.
The display module 10 comprises a display panel 11, a display driver or controller 12 and a flexible printed circuit (FPC) 15. The display module 10 is connected to a base band section 16 of the device via the flexible printed circuit 15. The base band section 16 comprises an engine 17, which is able to provide digital data for a respective image that is to be presented to a user. The display driver 12 receives image data from the base band engine 17 via the flexible printed circuit 15 and controls the display panel 11 accordingly.
When an electronic device comprising a display module is manufactured, it is usually checked on the production line whether the display module of the assembled or partially assembled device is functioning properly. This is currently realized by means of an electrical test and an additional visual test.
The electrical test can be used for checking whether a functioning connection has been established between a base band section and a display module. Such an electrical test is illustrated in FIG. 2.
FIG. 2 is a schematic block diagram, which presents like FIG. 1 the display module 10 and the base band engine 17, which are interconnected by an interface including the flexible printed circuit 15.
FIG. 2 shows some more details of the display driver 12. The display driver 12 comprises a frame memory 13 and a digital-to-analog-converter (DAC) 14. The frame memory 13 is linked via the DAC 14 to the display panel 11. Digital data for a respective image frame that is provided by the base band engine 17 via the interface to the display module 10 is stored in the frame memory 13. The DAC 14 converts the digital image data from the frame memory 13 into analog image data and writes it to the display panel 11.
For the electrical test, the base band engine 17 writes data to the frame memory 13 and reads the data from the frame memory 13 again, in order to verify whether the required connection is given.
The visual test is used in addition for checking whether the display panel 11 itself is working properly. This may include for instance checking whether all lines of the display panel 11 are working properly.
The visual test can be performed by a person or by test equipment, like a camera. It can be based on different kinds of predetermined test patterns that are presented on the display panel 11, for example a 1×1 checkerboard, a full white image, a full black image, etc.
Thus, two separate tests are needed for checking the display module. Further, visual tests are costly due to the required investments, time-consuming and error-prone.